Joule grows the microbes in photobioreactors that need no fresh water and occupy only a fraction of the land needed for biomass-based approaches. The creatures secrete fuel continuously, so it's easy to collect. Lab tests and small trials lead Afeyan to estimate that the process will yield 100 times as much fuel per hectare as fermenting corn to produce ethanol, and 10 times as much as making it from sources such as agricultural waste. He says costs could be competitive with those of fossil fuels.
If Afeyan is right, biofuels could become an alternative to petroleum on a much broader scale than has ever seemed possible. The supply of conventional biofuels, such as those made from corn, is constrained by the vast amount of water and agricultural land needed to grow the plants they're made from. And while advanced biofuels require less water and don't need high-quality land, their potential is limited by the expensive, multistep processes needed to make them. As a result, the International Energy Agency estimates that in 2050, biodiesel and ethanol will meet only 26 percent of world demand for transportation fuel.
http://www.technologyreview.com/energy/25077/?nlid=2916&a=f